The FreeBSD Diary

In a recent article, I described a dual opteron that I was setting up. I am now in the process of setting up the storage system for this baby. It is already decked out for SATA drives, so that is what I am going to use. This article deals mainly with the drive bays, the drive caddies, and finding out which drive bays relate to what SATA connectors.

This was not as easy as it sounds. Sure, if you've used these types of systems before, this article contains information that is very familiar to you. However, if you've never used a rack mountable chassis before, you'll learn as much as I did. Everything from finding the right screws to mount the drives, to figuring what drive bay is attached to what SATA cable connector.

The dual opteron is in a 2U case and has eight drive bays, four above, and four below. Each drive bay has a drive caddy, into which you mount a standard HDD. The drive caddies allow you to add and/or remove drives while the machine is still running. SATA, by design, is hot-swappable.

Removing the caddy

The drives are accessed by pressing a button on the left side of the caddy. This action pops out a lever, which releases the little clips which hold the drive securely in the drive bay.

The little clip that holds in the drive caddy can be seen in the above left photograph. As the lever is closed, the little clips pull the drive caddy tightly into the drive bay.

You can then pull the drive out of the drive bay, as you can see in the above center picture. It is really pretty cool the first time you do this to a running system. What is even more counter-intuitive, is putting new HDD into a powered-up system.

In the picture to the left, you can see a drive caddy has been completely removed from the system and is resting on the table. The are six screw holes that you can use to attach the drive to the drive caddy. Always use at least four screws. Six is better.

The photo to the right shows the inside of one of the drive bays. The top and bottom caddies have been removed. You can see the power connections on the left, and the data on the right. At the back of the photo is one of the fans of the row of fans that separate the drive compartment from the main board compartment of the server chassis.

To the left, you can see a drive attached to the drive caddy. As you can see, there is an empty screw hole on this side. In my collection of screws left over from other systems, I found only five screws that fit this particular situation. The screws need to have a very shallow head, otherwise they will extend above the drive caddy recess that holds the screw head. This would prevent the drive caddy from sliding into the drive bay.

With eight drives bays, and six screws each, I needed nearly 50 screws. I found them at my local computer recyclers, where 20 minutes of looking through three small bags of computer screws gave me what I needed. The head is very shallow, and flat. This is perfect for what I need.

50 screws sounds like a lot, but when you see them all in one place, it does not look so bad...

Each drive bay has lights at the front. Actually, they are not lights, but little bits of plastic that redirect the light from the back of the drive bay to the front of the caddy. You can see these "lights" in the photo to the right.

In this photo, you can see the end of the plastic light guides that fit up against the back plane. They look like two square bits of plastic, one above the other, on the right hand side of the drive caddy. To the left of the screw, you can see the guides as they traverse the length of the rail to the front of the drive caddy.

This photo shows another view of the same end of the rail. It is a very simple and clever solution without using wire and LEDs. It also keeps the cost of the caddies down.

This SATA drive has dual power connections. NOTE: you should only use one of the two power connectors. Using both will result in damage. No, this not personal experience. :)

From left to right, this photo shows the SATA power connector, the SATA data connector, the drive jumpers, and the traditional Molex power connector typical of IDE drives. The dual power connector approach on SATA drives is a transition feature. Most newer drives, including the 400GB drive delivered with the server, are dropping the traditional 4-pin Molex connector.

This photograph is a better view of the connections. On the left is the traditional power connection, then the drive jumpers, the SATA data connector, and finally the SATA power connector. You can see how the pins are staggered. This staggering is critical to hot-swapping.

3Ware (now part of AMCC) has donated a SATA II Hardware RAID Controller to this project. Today I received a 9550SX-8LP. This is a half length /low profile SATA II RAID Controller with 8 ports. 3Ware sent me the full kit, and their photograph (4.1MB) is here. The 3Ware photograph (532KB) of the card itself is here.

This photograph shows the SATA connectors on the card:

These are the product labels from the boxes:

3Ware also donated a Battery Backup Unit (BBU) (BBU-9550SX Kit). This unit is an add-on that allows the controller to use write-caching for optimal performance and not be exposed to data loss should a power failure occur. The battery supplies power to a memory module and when fully charged, can supply power for up to 72 hours. When the power is restored, cached data is flushed to disk.

The use of write caching allows the controller to immediately tell the OS that the write has been performed, allowing the OS to carry on. The controller will write the data later. This approach also allows the controller to make certain optimizations and further increase performance.

Now that I have the server and the RAID controller, I need some disks to hook up to it. If you happen to be in possession of eight SATA II drives with 16MB of cache, with a good performance record, I would love to hear from you. I'm sure we can come up with a good sponsorship arrangement that will benefit all parties concerned.

Once I have the HDD, I will hook them up and do some performance benchmarks, burn in the drives, and then deploy the server.

I thank iXsystems and 3Ware for their assistance in getting this server project off the ground. Their help and generous donations are greatly appreciated.